Japanese patent application No. 2000-98917 filed on Mar. 31, 2000 is hereby incorporated by reference in its entirety.
The present invention relates to a differential amplifier having two sets of differential amplifier circuits, a semiconductor device, a power supply circuit, and electronic equipment using the same.
A differential amplifier is shown in FIG. 8, which device has two, first and second differential amplifier circuits 210, 230. The first and second differential amplifier circuits 210, 230 are designed to receive first and second input voltages VIN1, VIN2 which have an offset therebetween. A P-type MOS transistor 250 is provided at the rear stage of the first differential amplifier circuit 210, which transistor is driven by a first signal S1 coming from the first differential amplifier circuit 210. Similarly, an N-type MOS transistor 252 is provided at the rear stage of the second differential amplifier circuit 230, which transistor is driven by a second signal S2 from the second differential amplifier circuit 230. These PMOS transistor 250 and NMOS transistor 252 are operable to pull together thus defining an output voltage VOUT.
As shown in FIG. 8 the first differential amplifier circuit 210 includes a P-type MOS transistor 212 and a P-type MOS transistor 214 that constitutes a current-mirror circuit together with the PMOS transistor 212.
The second differential amplifier circuit 230 includes an N-type MOS transistor 232 and an N-type MOS transistor 234 that makes up a current-mirror circuit together with the NMOS transistor 232.
The first differential amplifier circuit 210 further has an NMOS transistor 216 that is serially connected to the PMOS transistor 212 between power supply voltages VDD, VSS, and an NMOS transistor 218 as connected in series to the PMOS transistor 214 between the power supply voltages VDD, VSS. Additionally the NMOS transistors 216, 218 are coupled through a constant current source 220 to the power supply voltage VSS. These NMOS transistors 216, 218 are the same as each other both in size and in ability, and thus constitute a differential pair.
Similarly the second differential amplifier circuit 230 has a PMOS transistor 236 that is serially connected to the NMOS transistor 232 between the power supply voltages VDD, VSS and a PMOS transistor 238 as series-connected to the NMOS transistor 234 between power supply voltages VDD, VSS. The PMOS transistors 236, 238 are coupled to power supply voltage VDD via a constant current source 240. These PMOS transistors 236, 238 are the same in size and ability as each other, thus making up a differential pair.
According to one embodiment, there is provided a differential amplifier comprising:
a first differential amplifier circuit which operates based on a first input voltage and includes a first transistor of a primary conductivity type and a second transistor of the primary conductivity type which makes up a differential pair with the first transistor of the primary conductivity type;
a second differential amplifier circuit which operates based on a second input voltage and includes a first transistor of a secondary conductivity type and a second transistor of the secondary conductivity type which makes up a differential pair with the first transistor of the secondary conductivity type;
a third transistor of the secondary conductivity type which operates based on a first signal from the first differential amplifier circuit;
a third transistor of the primary conductivity type which is serially connected to the third transistor of the secondary conductivity type and operates based on a second signal from the second differential amplifier circuit; and
a voltage control circuit (first control circuit) which controls a voltage of a control terminal of the third transistor of the secondary conductivity type, based on a third signal from the second differential amplifier circuit,
wherein a voltage between the third transistor of the secondary conductivity type and the third transistor of the primary conductivity type is used as an output voltage.
According to another embodiment, there is provided a differential amplifier in which the first voltage control circuit is replaced by a second voltage control circuit which controls a voltage of a control terminal of the third transistor of the primary conductivity type based on a fourth signal from the first differential amplifier circuit.
According to further embodiment, there is provided a differential amplifier comprising both the first and second voltage control circuits described above. This makes it possible to accelerate the operation of both the third transistor of the secondary conductivity type and the third transistor of the primary conductivity type.
According to yet another embodiment, there is provided a power supply circuit comprising at least one such differential amplifier, or electronic equipment comprising such a power supply circuit.